Re: [PATCH v3 21/25] dax/region: Create resources on sparse DAX regions

[Ira Weiny]

Dave Jiang wrote:
> 
> 
> On 8/16/24 7:44 AM, ira.weiny@xxxxxxxxx wrote:
> > From: Navneet Singh <navneet.singh@xxxxxxxxx>
> > 

[snip]

> > diff --git a/drivers/cxl/core/extent.c b/drivers/cxl/core/extent.c
> > index d7d526a51e2b..103b0bec3a4a 100644
> > --- a/drivers/cxl/core/extent.c
> > +++ b/drivers/cxl/core/extent.c
> > @@ -271,20 +271,67 @@ static void calc_hpa_range(struct cxl_endpoint_decoder *cxled,
> >  	hpa_range->end = hpa_range->start + range_len(dpa_range) - 1;
> >  }
> >  
> > +static int cxlr_notify_extent(struct cxl_region *cxlr, enum dc_event event,
> > +			      struct region_extent *region_extent)
> > +{
> > +	struct cxl_dax_region *cxlr_dax;
> > +	struct device *dev;
> > +	int rc = 0;
> > +
> > +	cxlr_dax = cxlr->cxlr_dax;
> > +	dev = &cxlr_dax->dev;
> > +	dev_dbg(dev, "Trying notify: type %d HPA %par\n",
> > +		event, &region_extent->hpa_range);
> > +
> > +	/*
> > +	 * NOTE the lack of a driver indicates a notification has failed.  No
> > +	 * user space coordiantion was possible.
> > +	 */
> > +	device_lock(dev);
> > +	if (dev->driver) {
> > +		struct cxl_driver *driver = to_cxl_drv(dev->driver);
> > +		struct cxl_notify_data notify_data = (struct cxl_notify_data) {
> > +			.event = event,
> > +			.region_extent = region_extent,
> > +		};
> > +
> > +		if (driver->notify) {
> > +			dev_dbg(dev, "Notify: type %d HPA %par\n",
> > +				event, &region_extent->hpa_range);
> > +			rc = driver->notify(dev, &notify_data);
> > +		}
> > +	}
> > +	device_unlock(dev);
> 
> Maybe a cleaner version:
> 	guard(device)(dev);
> 	if (!dev->driver || !dev->driver->notify)
> 		return 0;

There is no dev->driver->notify.  But this works.

        if (!dev->driver)
                return 0;
        driver = to_cxl_drv(dev->driver);
        if (!driver->notify)
                return 0;

Not quite as clean but I did miss the use of guard.

> 
> 	dev_dbg(...);
> 	return driver->notify(dev, &notify_data);
>

I've cleaned it up.

[snip]

> > +
> > +int dax_region_add_resource(struct dax_region *dax_region,
> > +			    struct device *device,
> > +			    resource_size_t start, resource_size_t length)
> >
> kdoc header?

Because dax_region_add_resource() is part of the DAX private interfaces
and not intended to be used outside the DAX subsystem I skipped the kdoc
here even though the function must be exported.  Same for
dax_region_rm_resource() and dax_avail_size().

This is similar to run_dax() in that it is designed as a 'generic
operation' within the dax subsystem but not generally useful to the
kernel.

For now I'll move their declarations in dax-private.h and make a similar
comment.

Ira

> 
>  +{
> > +	struct resource *new_resource;
> > +	int rc;
> > +
> > +	struct dax_resource *dax_resource __free(kfree) =
> > +				kzalloc(sizeof(*dax_resource), GFP_KERNEL);
> > +	if (!dax_resource)
> > +		return -ENOMEM;
> > +
> > +	guard(rwsem_write)(&dax_region_rwsem);
> > +
> > +	dev_dbg(dax_region->dev, "DAX region resource %pr\n", &dax_region->res);
> > +	new_resource = __request_region(&dax_region->res, start, length, "extent", 0);
> > +	if (!new_resource) {
> > +		dev_err(dax_region->dev, "Failed to add region s:%pa l:%pa\n",
> > +			&start, &length);
> > +		return -ENOSPC;
> > +	}
> > +
> > +	dev_dbg(dax_region->dev, "add resource %pr\n", new_resource);
> > +	dax_resource->region = dax_region;
> > +	dax_resource->res = new_resource;
> > +	dev_set_drvdata(device, dax_resource);
> > +	rc = devm_add_action_or_reset(device, dax_release_resource,
> > +				      no_free_ptr(dax_resource));
> > +	/*  On error; ensure driver data is cleared under semaphore */
> > +	if (rc)
> > +		dev_set_drvdata(device, NULL);
> > +	return rc;
> > +}
> > +EXPORT_SYMBOL_GPL(dax_region_add_resource);
> > +
> > +int dax_region_rm_resource(struct dax_region *dax_region,
> > +			   struct device *dev)
> 
> kdoc header
> > +{
> > +	struct dax_resource *dax_resource;
> > +
> > +	guard(rwsem_write)(&dax_region_rwsem);
> > +
> > +	dax_resource = dev_get_drvdata(dev);
> > +	if (!dax_resource)
> > +		return 0;
> > +
> > +	if (dax_resource->use_cnt)
> > +		return -EBUSY;
> > +
> > +	/* avoid races with users trying to use the extent */
> > +	__dax_release_resource(dax_resource);
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(dax_region_rm_resource);
> > +
> >  bool static_dev_dax(struct dev_dax *dev_dax)
> >  {
> >  	return is_static(dev_dax->region);
> > @@ -296,19 +373,44 @@ static ssize_t region_align_show(struct device *dev,
> >  static struct device_attribute dev_attr_region_align =
> >  		__ATTR(align, 0400, region_align_show, NULL);
> >  
> > +#define for_each_child_resource(extent, res) \
> > +	for (res = (extent)->child; res; res = res->sibling)
> > +
> > +resource_size_t
> > +dax_avail_size(struct resource *dax_resource)
> kdoc header
> 
> DJ
> 

[snip]